Microphone assembly



March e; M. GIANNINI MICROPHONE ASSEMBLY Original Filed March 22, 1943 INVENTOR. GABRIEL M. GIANNINI ATTORN EYS Patented Mar. 2, 1948 MICROPHONE ASSEMBLY).

Gabriel M. Giannini, West Los Angeles, Calif assignor, by mesne assignments, to Automatic Electric Laboratories,

poration of Delaware Claims. 1

The present invention relates to microphone assemblies and more particularly to such microphone assemblies adapted for use in sound direction finders of the electro-acoustic or microphone type. This application is a division of the copending application of Gabriel M. Giannini, Serial No. 480,028, filed March 22, 1943, now Patent No. 2,417,927, granted March 25, 1947.

It is an object of the present invention to provlde a microphone assembly which is of compact and economical construction and arrangement and which is highly efficient in operation.

A further object of the invention is to provide a microphone assembly which is of improved con struction and arrangement lending'the microphone assembly particularly suitable for use upon a submarine or other submersible device.

Further features of the invention pertain to the particular construction and arrangement of the mechanical andelectrical elements of the microphone assembly, whereby the above-cu"- lined and additional operating advantages are attained.

The invention both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the following specification taken in connection with the accompanying drawing, in which Figure 1 is a plan sectional view of a microphone assembly particularly adapted for use in a sound direction finder; and Fig. 2 is a longitudinal sectional view of the microphone assembly shown in Fig. 1.

Referring now more particularly to Figs. 1 and 2 of the drawing, the microphone assembly Sill there illustrated is particularly adapted for use in a sound direction finder which is arranged to be supported by the periscope of a submarine or other submersible craft or by a diving bell or the like. The microphone assembly comprises a base 30! which is adapted to be directly secured to the periscope or other rotatable part and a substantially bell-shaped casing till! hermetically sealed to the base 385, thecasing 3532 including a removable dome 5&3 hermetically sealed thereto. The interior of the casing 3.92 is hollow and carries a substantially centrally disposed supporting ring 3M upon which is mounted an upstanding annular frame 3ll5, the frame 355 being mounted upon the supporting ring 3% by means of a mounting ring 3% formed of rubber or the like, whereby the frame 3% is resiliently supported by the supporting ring 384. One end of the frame 3E5 is hermetically sealed by an arrangement comprising a substantially semitween the frame 355 and the diaphragms Inc., Chicago, 111., a cor- 2 spherical and inwardly directed diaphragm till, a substantially semi-spherical and inwardly directed reticulated screen 3&8, an intervening spacing ring 3%, and a clamping ring 316], the reticulated screen 3% directly engaging the adjacent end of the frame 3&5, the spacing ring 3653 being disposed between the peripheral portions of the reticulated screen 338 and the diaphragm Sill and the clamping ring 330 directly engaging the adjacent peripheral portion of the diaphragm Sill. The elements named are retained in assembled relation by screws or the like, not shown, whereby the adjacent end mentioned of the frame 395 is hermetically sealed. Similarly, the other end of the frame 365 is hermetically sealed by an arrangement comprising a substantially semispherical and inwardly directed diaphragm 3i i, a substantially semispherical and inwardly directed reticulated screen M2, an intervening spacing ring 3l3, and a clamping ring aid, the reticulated screen 312 directly engaging the adiacent end of the frame 385, the spacing ring 353 being disposed between the peripheral portions of the reticulated screen 3B2 and the diaphragm 3H and the. clamping ring 314 directly engaging the adjacentperipheral portion of the diaphragm 3. The elements named are retained in assembled relation by screws or the like, not shown, whereby the adjacent end mentioned of the frame 335 is hermetically sealed.

Accordingly, the two inwardly directed reticulated screens 368 and'3 l 2 are respectively spaced with respect to the associated diaphragms 3t? and 3 to protect the diaphragms mentioned and are disposed substantially in contact with each other adjacent the centers thereof at the approximate center of the frame Also a substantially centrally disposed conduit did is arranged within a recess es in formed in the base 33! and projects through an opening provided the top wall of the base 39 l, the upper end of the conduit 3l5 being flared outwardly to provide a substantially cone-shaped throat .326 secured a cooperating conical opening provided in the bottom of the frame 335, whereby the interior the compartment defined between the frame 365 and the cooperating diaphragms 3N and Eli communicates through the conduit 335 with the exterior. Also a breather tube 3!? is arranged within the conduit Bid and extends toward the top of the compartment mentioned defined bo-- 3t! and St I, the breather tube 3i? having an ofiset central portion disposed out of contact with re spect 'to the reticulated screens 36% and 352,

whereby the interior of the compartment mentioned may be vented through the breather tube 3|1. Thebreather tube 3" is suitably supported in the throat 3|6 of the conduit 3|5 by an associated plug 3l8, the breather tube 3" extending through an opening formed in the plug 3|8 and the plug 3|8 having other openings therein directly connecting the interior of the compartment formed between the frame 305 and the diaphragms 301 and 3H and the interior of the throat 3|6 of the conduit 3|5.

The diaphragm 301 forms a part of a first microphone which also includes a substantially C- shaped field structure 3|9 carrying a winding or coil 320, the field structure 3|9 being suitably secured to the clamping ring 310 by a number of blocks or wedges 32| illustrated. The diaphragm 301 is formed of magnetic material while the field structure 3|9 comprises a permanent magnet arranged in spaced relation with respect thereto, whereby a magnetic field is normally set up between the north and south poles of the permanent magnet 3|9 which includes the adjacent section of the diaphragm 301. Also the blocks 32| disposed between the permanent magnet 3|3 and the clamping ring 3|0 are formed of. nonmagnetic material, thereby to prevent flux leakage between the top and bottom portions of the permanent magnet 3|9 and the adjacent peripheral portion of the diaphragm 301. The first microphone, comprising the permanent magnet 3| 9 and the coil 320, is embedded in a molded block 322 formed of rubber or the like and filling a portion of the interior of the casing 302 dis posed between the clamping ring 3| and the adjacent inner side wall of the casing 302. The block 322 has a number of openings 323 formed therein out of contact with the permanent magnet 3|9 and the coil 320 and communicating between a chamber 324 defined between the block 322 and the adjacent surface of the diaphragm 301, the openings 323 also communicating through openings 325 formed in the casing 302. Accordingly, the chamber 324 defined between the diaphragm 301 and the block 322 communicates with the exterior through the openings 323 formed in the block 322 and the openings 325 formed in the casing 302.

Similarly, the diaphragm 3|| forms a part of a second microphone which also includes a substantially C-shaped field structure 323 carrying a winding or coil 321, the field structure 326 being suitably secured to the clamping ring 3 4 by a number of blocks or wedges 328 illustrated. The diaphragm 3 is formed of magnetic material while the field structure 326 comprises a permanent magnet arranged in spaced relation with respect thereto, whereby a magnetic field is normally set up between the north and south poles of the permanent magnet 326 which includes the adjacent section of the diaphragm 3| Also the blocks 328 disposed between the permanent magnet 326 and the clamping ring 3M are formed of the nonmagnetic material, thereby to prevent flux leakage between the top and bottom portion of the permanent magnet 326 and the adjacent peripheral portion of the diaphragm 3| The second microphone, comprising the permanent magnet 326 and the coil 321, is arranged within an air filled cavity 329 formed in the casing 302 adjacent the diaphragm 3. Finally a terminal block 330 is provided which is supported in a recess formed in the frame 305; which terminal block terminates the coils 320 and 321. Finally it is noted that the terminal block 330 may be electrically connected through the compartment formed between the frame 335 and the diaphragms 301 and 3| the plug 3H] and the conduit M5 to the exterior. Preferably, the two microphones are wired in opposition to eachother, whereby the microphone assembly 300 is of the balance type.

Considering now the operation of the microphone assembly 300 after the supporting craft or the like has reached the surface, the periscope or other support upon which the sound direction finder 330 is mounted is projected into the air and is rotated by any suitable means. At this point it is noted that any water entering the chamber 320 defined between the diaphragm 301 and the block 322 through the openings 323 is drained therefrom after the microphone assembly 330 is positioned in the associated atmosphere; and that such water has no deleterious effect upon the second microphone due to the water impervious nature of the material of which the block 322 embedding the elements of the second microphone is formed. At this time the chamber 320 formed adjacent the diaphragm 361 and the block 322 is directly connected via the openings 323 to the atmosphere; while the cavity 329 disposed adjacent the diaphragm 3|| of the second microphone is shielded by the side Wall of the casing 302. Hence, the first microphone will produce a greater output than the second microphone, assuming that the same intensity of sound is reaching the diametrically disposed surfaces of the casing 302, as will be readily appreciated. At this time the base 33! and consequently the casing 302 are rotated until a maximum output is obtained from the two balanced connected microphones. At this time the first microphone comprising the permanent magnet 3|3 and the coil 326 is directed toward the source of sound, whereby the associated apparatus, through which microphone assembly 300 carried by the sound direction finder is revolved, is operative to indicate the direction of the source of sound in ordinary compass values, in the manner previously explained.

While the preferred embodiments of the invention have been disclosed, it will be understood that various modifications may be made therein which are within the true spirit and scope of the invention.

What is claimed is:

1. A microphone assembly comprising a casing, a frame disposed in said casing, a first diaphragm supported by one side of said frame, a second diaphragm supported by the other side of said frame, first magnetic structure disposed between said first diaphragm and one side wall of said casing and cooperating with said first diaphragm, a first winding coupled to said first magnetic structure, second magnetic structure disposed between said second diaphragm and the other side wall of said casing and cooperating with said second diaphragm, a, second winding coupled to said second magnetic structure, and a block of water impervious material sealing said one side of said frame to said one side wall of said casing and embedding said first magnetic structure and said first winding, said block being spaced from said first diaphragm to define a chamber therebetween and having sound passages formed therein out of contact with said first magnetic structure and said first winding and communicating between said chamber and the exterior through connecting openings provided in said one side wall of said casing, whereby said first diaphragm communicates directly with sound from the exterior, said other side wall of said casing partially shielding said second diaphragm from sound from the exterior.

2. A microphoneassembly comprising a casing, a frame disposed in said casing, a first diaphragm sealed to one side of said frame, a second diaphragm sealed to the other side of said frame, said frame and said first and second diaphragms defining a compartment within said casing, a breather conduit extending through an aperture provided in said casing and communicating be tween said compartment and the exterior, first magnetic structure disposed between said first diaphragm and one side wall of said casing and cooperating with said first diaphragm, a first winding coupled to said first magnetic structure, second magnetic structure disposed between said second diaphragm and the other side wall of said casing and cooperating with said second diaphragm;a second winding coupled to said second magnetic structure, and a block of water impervious material sealing said one side of said frame to said one side wall of said casing and embedding said first magnetic structure and said first winding, said block being spaced from said first diaphragm to define a chamber therebetween and having sound passages formed therein out of contact with said first magnetic structure and said first winding and communicating between said chamber and the exterior through connecting openings provided in said one side wall of said casing, whereby said first diaphragm communicates directly with sound from the exterior, said other side wall of said casing partially shielding said second diaphragm from sound from the exterior.

3. A microphone assembly comprising a casing, a frame disposed in said casing, a diaphragm supported by said frame, magnetic structure disposed between said diaphragm and one wall of said casing and cooperating with said diaphragm, a Winding coupled to said magnetic structure, and a block of water impervious material sealing said frame to said one wall of said casing and embedding said magnetic structure and said winding, said block being spaced from said diaphragm to define a chamber therebetween and having sound passages formed therein out of contact with said magnetic structure and said winding and communicating between said chamber and the exterior through connecting openings provided in said one wall of said casing.

4. A microphone assembly comprising a casing, a frame disposed in said casing, a diaphragm supported by said frame, magnetic structure disposed between said diaphragm and one wall of said casing and cooperating with said diaphragm, a winding coupled to said magnetic structure, and a block of rubber molded into direct contact with said frame and said one Wall of said casing and into embedding relation with said magnetic structure and said winding, whereby a water im pervious seal is provided between said frame and said one wall of said casing, said block being spaced from said diaphragm to define a chamber therebetween and having sound passages formed therein out of contact with said magnetic structure and said winding and communicating between said chamber and the exterior through connecting openings provided in said one wall of said casing.

5. A microphone assembly comprising a casing, a frame disposed in said casing and resiliently supported thereby, a diaphragm supported by said frame, magnetic structure disposed between said diaphragm and one Wall of said casing and supported by said frame and cooperating with said diaphragm, a winding supported by said magnetic structure and coupled thereto, and a block of Water impervious material sealing said frame to said one wall of said casing and embedding said magneticstructure and said winding, said block being spaced from said diaphragm to define a chamber therebetween and having sound passages formed therein out of contact with said magnetic structure and said winding and communicating between said chamber and the exterior through connecting openings provided in said one wall of said casing.

' GABRIEL M. GIANNINI.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,402,546 Steinberger Jan. 3, 1922 1,634,292 Lederer July 5, 1927 

